Thermionic valve



I Dec. 9, 1952 L 7 2,621,310

' THERMIONIC VALVE Filed June 1, 1949 2 SHEETSSHEET l mvenrro Jqm Enq'r'roR NEY Dec. 9, 19.52 J. BELL 2,621,310

THERM'IONIC VALVE Filed June 1, 1949 2 SHEETSSI-IEET 2 INVENTQR L/HM'SFETTORNEY Patented Dec. 9, 1952 THERMIONIC VALVE James Bell, Pinner,England, assignor to The Fri-O Valve Company Limited, LondomEnglandAppiication June 1, 1949, Serial No.f96,429 In Great Britain May 24,1948 2 Claims.

The present invention relates to a thermionic valve type oscillator foroperation at high frequencies, for example, frequencies of the order ofone thousand megacycles per second.

It is well known that thermionic valves for operation at highfrequencies are provided in which a control grid electrode is mounted ona disc-seal, so that in the case of a triode valve, for example, thedisc-seal is earthed in operation and thus provides substantialscreening between the anode and the cathode, the anode and the cathodelying on opposite sides of the disc-seal.

When it is required to use such a disc-seal valve as an oscillator withthe control grid electrode common to the two portions of the oscillatorycircuit, however, it sufiers from the disadvantage that the capacitancebetween the anode and the cathode inside the valve is usually too smallto provide sufiicient feed-back in the associated oscillatory circuit tosustain oscillations.

The object of this invention is to overcome the above disadvantage whileretaining the advantages of low electrode-lead inductance obtained bythe use of the disc-seal form of construction.

According to the present invention a high frequency oscillator isprovided including a thermionic valve having at least an anode, acathode and a control electrode all contained in an envelope, the anodebeing supported by a metal disc sealed through the walls of the envelopein such manner that the seals of the respective lead-in connectionsthrough the envelope to the cathode and control electrode lie onopposite sides of the disc, the oscillator having two high frequencyresonant circuits associated therewith, the first of which is connectedbetween the disc and lead-in connection to the cathode, and the secondof which is connected between the disc and lead-in connection to thecontrol electrode.

One arrangement according to the present invention will now bedescribed, by way of example, with reference to the accompanyingdrawings, in which:

Figure 1 shows a diagrammatic central sectional view of a thermionicvalve for use in an oscillator according to the invention; and

Figure 2 shows a coaxial-line circuit suitable for use with a thermionicvalve such as is shown in Figure 1 parts of the outer conductors of thecircuit being cut away to show internal details.

Referring to Figure 1, the valve is provided with a cylindrical glassenvelope I through one end of which is sealed a hollow metal cylinder 2which supports a hollow cylindrical nickel cathode 3, the envelope I,cylinder 2, and cathode '2 3 all being coaxial. the end furthest fromthe cylinder 2 and its outer longitudinal surface is provided with a.

suitable electron-emissive oxide coating. The cathode 3 is provided witha spiral heater 4, one end of which is connected to the cathode '3. Theother end of the heater 4 is connected to a lead 5 which is disposedalong the axis of the cylinder 2 and which is connected to .a hollowmetal pin 5 sealed into the outermost end of cylinder 2 by means of aninsulating plug '7. The interior of the cylinder 2 is sealed by means ofa glass plug -8.

The control electrode is in the form of .a squirrel-cage grid 9 mountedso that it surrounds the cathode 3 .coaxially. Thegrid 9 is supported bymeans of .an annular .copper disc II! disposed perpendicularly to thelongitudinal axis of the grid 9. The disc I0 is sealed through the.envelope I in the conventional manner to provide the lead-in connectionto the control electrode.

The anode consists of a hollow open-ended copper cylinder I I disposedcoaxially around the grid 9. The cylinder II forms an integral part of asecond copper disc I2, which is disposed parallel to the disc [0 and issealed through the envelope I in the conventional manner to provide thelead in connection to the anode. Attached to the disc I2 by means oftags I3 is a cylindrical metal shield I4 which is partially closed atthe end further from the disc I2. The shield I4 serves to preventdeposition on the envelope I of any material evaporated from thecylinder 2 during operation of the valve.

The discs I0 and I2 are provided with flanges I5 and I6 respectively forthe purpose of locating the valve accurately when it is plugged into anassociated circuit.

Referring now to Figure 2, the circuit is made in two portions, ananode-cathode circuit having outer and inner conductors I! and I8respectively, and an anode-grid circuit having outer and innerconductors I9 and 20 respectively. The anode cathode and anode-gridcircuits are respectively tuned by means of fingered pistons 2| and 22.

The end of the conductor I8 is enlarged into a hollow cylindrical cup 23into which the outer end of cylinder 2 is designed to fit when the valveis plugged into the circuit. The metal pin 6 is adapted to connect witha heater lead (not shown) which runs along the interior of conductor I8,the heater lead and conductor I8 being insulated from each other. Theconductor I! has an internal diameter greater than the external diameterof the envelope I, and is pro- The cathode 3 is closed at vided at oneend with an external flange made in two parts, 24 and 25, separated byan annular mica sheet 26.

The end of conductor 20 is also hollow and is provided with fingers 21which are adapted to contact the flange [5 of the grid disc in when thevalve is plugged into the circuit. The conductor I9 is provided with anannular end plate made in two parts 28 and 29, separated by an annularmica sheet 39. The central hole 3| of part 29 is of such a diameter thatwhen the valve is plugged into the circuit, the flange I5 of the anodedisc l2 contacts the surface of the hole 3|.

The part 25 is provided with four teeth 32, 33, 34, 35 which are adaptedto slide under four arcuate plates 36, 37, 38, 39 attached to part 29when the outer faces of parts 25 and 29 are brought into contact and thetwo portions of the circuit are rotated relative to one another abouttheir longitudinal axes. The two portions of the circuit may thus beheld together with the outer portion of the anode disc 12 clampedbetween the parts 25 and 29. The plate 31 is turned over at one cornerto provide a stop.

It will be seen that when the circuit is assembled with a valve pluggedin it, the anode disc I2 is electrically connected to the outerconductors H and 9 for alternating current, but not for direct current.Connection to the anode may be made by means of a tag 40 attached to theend plate of the grid-anode circuit.

It will be appreciated that a valve in an oscillator according to thepresent invention can be made with adequate capacitance between thecathode and control electrode to provide sufficient feed-back to sustainoscillation whilst at the same time making use of the disc-seal form ofconstruction.

What I claim is:

1. A high frequency oscillator comprising a thermionic valve having acathode, a control electrode and an anode all contained in an envelope,a metal disc sealed through the walls of the envelope and supporting theanode, a leadin connection through the envelope to the oathode disposedon one side of the disc, and a leadin connection through the envelope tothe control electrode disposed on the opposite side of the disc, a firsttunable coaxial line circuit having its outer conductor capacitivelycoupled to the disc and its inner conductor connected to the lead-inconnection to the cathode, and a second tunable coaxial line circuithaving its outer conductor capacitively coupled to the disc and itsinner conductor connected to the lead-in connection to the controlelectrode.

2. A high frequency oscillator according to claim 1, in which thelead-in connection to the control electrode comprises a second metaldisc sealed through the walls of the envelope and supporting the controlelectrode.

JAMES BELL.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,320,941 Litton June 1, 19432,395,043 Goodchild Feb. 19. 1946 2,404,363 Chevigny July 23, 19462,446,829 Hergenrother Aug. 10, 1948 2,461,125 Nergaard Feb. 8, 1949

